A storage cell, such as a nickel-cadmium (NiCad) cell or a lithium ion cell, typically loses its charge over a period of time, primarily as result of a self-discharge current that occurs in the storage cell. Unfortunately, given the current state of the art, it is practically impossible to completely eliminate the self-discharge current in these storage cells. Furthermore, while there has been a limited level of success in testing individual storage cells in a laboratory environment, it is turning out to be quite complex and impractical to measure the self-discharge current characteristics of each of a batch of storage cells in a manufacturing environment.
More particularly, measuring the self-discharge current parameters of each of a batch of lithium ion cells during manufacture is turning out to be impractical due to a variety of reasons. Some of these reasons include shortcomings associated with existing lithium storage cell technologies, while other shortcomings are associated with commercially available potentiostat systems used for carrying out these types of measurements. The shortcomings associated with commercially available potentiostat systems, particularly those used for characterizing lithium ion cells that are larger than button cells, can include complexity, insufficient accuracy, and undesirably high cost.
Consequently, in lieu of batch testing lithium ion cells on a manufacturing floor, some test entities have opted to use an alternative approach wherein an open circuit voltage of each of a batch of lithium ion cells is measured prior to storing the batch of lithium ion cells in a controlled temperature facility. In many cases, the storage period can extend to a couple of weeks or longer. Upon completion of the storage period, the open circuit voltage of each lithium ion cell is measured once again in order to evaluate the self-discharge current characteristics of each lithium ion cell on the basis of a drop in the open circuit voltage as a result of the storage. As can be understood, not only does such a procedure merely provide an approximation of the self-discharge current characteristic of each lithium ion cell but also suffers from various other shortcomings such as the testing period having to extend over a couple of weeks or longer, storage requirements (including controlled environmental conditions), and potential hazards (fire hazard, chemical leaks, toxic emissions etc.) during storage.